An in-situ laser analysis technology (including LIBS and LA-ICP-MS) is a technology capable of realizing in-situ sampling in a micron area, combines laser ablation and spectrum or plasma mass spectrometry and may realize analysis of content of primary trace elements or isotope composition in a sample. In recent years, the technology is widely applied to the fields of geoscience, modern science and technology archaeology, material science, bioscience and the like.
The in-situ laser analysis technology focuses the laser on a sample surface to ablate the sample by virtue of a light path, analyzes plasma generated by ablation to obtain an LIBS spectral signal, and conducts mass spectrometry on aerosol generated by ablation to obtain an ion signal; and the two signals may be complementary to each other, so that the content of the primary trace elements or the isotope composition is obtained to perform element distribution law or isotopic tracing, labeling and other studies, such as a study on a poisoning mechanism of heavy metals in animal brains and livers, a study on sources of heavy metal pollutants in soil, a study on element and isotopic geochemical tracing for formation and evolution of the earth, a history of civilization on element and isotope composition tracing in archaeological samples of bronze ware, ceramics and the like, etc.
In the in-situ laser analysis, a process that the laser acts on the sample is performed in a sample chamber, while key factors that influence the reliability of results of the in-situ laser analysis technology include a heat effect that acts on the sample surface by the laser in a process of ablating the sample by the laser, and an elemental fractionation effect caused by different ablation efficiencies of different elements/isotopes in the sample due to a transmission efficiency difference of the aerosol generated by ablation. The key factor that influences the stability of the results of the in-situ laser analysis technology includes instability of a subsequent plasma ion source caused by air (particularly oxygen) introduced in a sample replacement process. The heat effect of the laser may be solved by changing the pulse width of a laser device.
At present, a sample loading apparatus for laser ablation is generally as follows: a glass window through which the laser can pass is formed in a circular sample chamber, or a small inner chamber is formed in a larger sample chamber. The previous sample chamber has a small volume, and generally may simultaneously load one sample target and one standard target only. Moreover, if samples have different positions in the sample chamber, the aerosol transmission efficiency is often influenced and a severe fractionation effect is caused, thereby influencing accuracy of the analysis result. With respect to the latter sample chamber, since the main sample chamber is large and the small sample chamber is close to an upper side, air in the main sample chamber is difficult to be completely replaced with carrier gas (generally helium); and oxygen which is slowly released in the sample target and the carrier gas will be gradually accumulated in the main sample chamber, causing the gradual increase of spectral interference caused by the oxygen, so that baselines of partial elements are gradually elevated in the analysis process (e.g., a signal that 16O16O interferes with 32S, a signal that 16O40Ar interferes with 56Fe, and the like). A signal to noise ratio is influenced; analytical accuracy of the content of interfered elements and an isotope ratio is poor; and a detection limit is decreased. Therefore, it is necessary to improve the above defects.